[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Nervous system and senses](https://durgical.com/en/embryology/#a-nervous) › Congenital hearing loss, microtia and preauricular pits [Embryology](https://durgical.com/en/embryology/) · [Nervous system and senses](https://durgical.com/en/embryology/#a-nervous) # Congenital hearing loss, microtia and preauricular pits - Malformation Some babies are born not hearing well, with a small ear or with a tiny pit in front of the ear; all of them deserve a hearing test. Updated 2026-11-01 **See it in 3D:** [Auricle](https://durgical.com/en/anatomy/auricle/) · [Ear canal](https://durgical.com/en/anatomy/external-acoustic-meatus/) · [Eardrum](https://durgical.com/en/anatomy/tympanic-membrane/) · [Malleus](https://durgical.com/en/anatomy/malleus/) · [Incus](https://durgical.com/en/anatomy/incus/) · [Stapes](https://durgical.com/en/anatomy/stapes/) · [Cochlea](https://durgical.com/en/anatomy/cochlea/) · [Vestibulocochlear nerve (VIII)](https://durgical.com/en/anatomy/vestibulocochlear-nerve/) ## Key points - Sensorineural = inner ear; conductive = external or middle ear. - GJB2 (connexin 26): most common genetic cause of nonsyndromic deafness. - Congenital CMV: a major non-genetic cause; it can be late-onset. - Microtia with atresia: conductive loss; isotretinoin is a known cause. - Preauricular pit or tag: test hearing. ## What it is Congenital hearing loss can be sensorineural (hair cells or nerve, from the inner ear) or conductive (canal, eardrum or ossicles). Microtia is a small, malformed auricle, often with canal atresia; preauricular pits and tags are remnants of the auricular hillocks. Any of them is a clue to look for other malformations and a reason for newborn hearing screening. ## Key facts - Congenital hearing loss: about 2 to 3 per 1000 births; about half is genetic. - GJB2 (connexin 26) variants cause about half of autosomal recessive nonsyndromic deafness. - Congenital CMV: a common infectious cause; hearing loss can appear after a normal screen. - Other causes: rubella, prematurity, maternal diabetes, retinoids (isotretinoin). - Microtia: types 1 (small, normally shaped ear) to 4 (anotia); usually one-sided; about 1 in 3800 US births. - Preauricular pits: common and usually harmless; they can become infected. ## Embryological cause - Sensorineural: failure of the otic vesicle, of organ of Corti hair cells or of the vestibulocochlear ganglion. - Conductive: defects of the first cleft (canal atresia), the tympanic membrane or the ossicles of arches 1 and 2. - Microtia: the six auricular hillocks (arches 1 and 2, with neural crest) do not grow or fuse properly in weeks 6–8. - Preauricular pit: incomplete fusion of the hillocks; tags come from accessory hillocks. - Because the auricle depends on neural crest, its defects travel with face, kidney or heart anomalies. ## Markers - GJB2 - SLC26A4 - EYA1 - HOXA2 ## How it presents - Hearing loss: failed newborn screen, a baby who does not react to sounds, delayed speech. - Microtia: small auricle, often with a narrow or absent canal and conductive loss on that side. - Microtia associations: oculo-auriculo-vertebral spectrum, oral clefts, facial asymmetry, kidney and heart anomalies. - Pits and tags: in front of the tragus; discharge or swelling may mean an infected tract. ## Diagnosis - Newborn hearing screening with otoacoustic emissions or automated auditory brainstem response. - Audiology referral if the screen fails or if there is microtia, a pit or a tag. - CMV testing in the first weeks of life if the hearing screen fails. - Temporal bone CT to plan canal surgery; kidney ultrasound if other findings are present. ## Memory aid 'If the outside of the ear looks odd, check inside and below': hearing, face and kidneys. ## Test yourself Think of the answer, then tap the question to see it. ## Which gene is the most common genetic cause of nonsyndromic deafness? GJB2, which encodes connexin 26. ## What type of hearing loss does microtia with canal atresia cause? Conductive hearing loss, because sound cannot reach the middle ear. ## Why does microtia prompt a search for other malformations? Because the auricle depends on neural crest of arches 1 and 2, which also builds the face and contributes to other organs. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/embryology/congenital-hearing-loss-microtia-and-preauricular-pits/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Auricle](https://durgical.com/en/anatomy/auricle/) - [Ear canal](https://durgical.com/en/anatomy/external-acoustic-meatus/) - [Eardrum](https://durgical.com/en/anatomy/tympanic-membrane/) - [Malleus](https://durgical.com/en/anatomy/malleus/) - [Incus](https://durgical.com/en/anatomy/incus/) - [Stapes](https://durgical.com/en/anatomy/stapes/) - [Cochlea](https://durgical.com/en/anatomy/cochlea/) - [Vestibulocochlear nerve (VIII)](https://durgical.com/en/anatomy/vestibulocochlear-nerve/) ## Related - [Ear: inner, middle and external ear](https://durgical.com/en/embryology/ear-inner-middle-and-external-ear/) - [Pharyngeal clefts and membranes: external ear and cervical sinus](https://durgical.com/en/embryology/pharyngeal-clefts-and-membranes-external-ear-and-cervical-sinus/) - [First-arch syndromes: Treacher Collins and Pierre Robin sequence](https://durgical.com/en/embryology/first-arch-syndromes-treacher-collins-and-pierre-robin-sequence/) - [Congenital rubella syndrome](https://durgical.com/en/embryology/congenital-rubella-syndrome/) - [TORCH infections: what each agent does to the embryo and fetus](https://durgical.com/en/embryology/torch-infections-what-each-agent-does-to-the-embryo-and-fetus/) - [Isotretinoin and other retinoids](https://durgical.com/en/embryology/isotretinoin-and-other-retinoids/) - [Neural crest cells and their derivatives](https://durgical.com/en/embryology/neural-crest-cells-and-their-derivatives/) ## Related conditions - [Hearing loss (conductive and sensorineural, including sudden hearing loss)](https://durgical.com/en/conditions/hearing-loss/) - [Congenital (TORCH) infections: syphilis, toxoplasmosis, CMV and Zika](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/) ## Microorganisms - [Cytomegalovirus](https://durgical.com/en/microbiology/cytomegalovirus/) - [Rubella virus](https://durgical.com/en/microbiology/rubella-virus/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Anotia/Microtia](https://www.cdc.gov/birth-defects/about/anotia-microtia.html) (Centers for Disease Control and Prevention, 2024); [Ear tag: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003304.htm) (U.S. National Library of Medicine, 2024); [Nonsyndromic hearing loss: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/nonsyndromic-hearing-loss/) (U.S. National Library of Medicine, 2024); [CMV in Newborns](https://www.cdc.gov/cytomegalovirus/congenital-infection/index.html) (Centers for Disease Control and Prevention, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/congenital-hearing-loss-microtia-and-preauricular-pits/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/congenital-hearing-loss-microtia-and-preauricular-pits/